1. Field of the Invention
The present invention relates to a method and apparatus for removing an electronic component, such as a semiconductor device, from a board to which the component is secured with resin. The invention also relates to manufacture of electronic apparatus in which a defective component is removed from a wiring board.
2. Description of the Prior Art
In recent years, plastic material packages have been widely used with the improvement of the reliability of semiconductor devices, and semiconductor devices bonded with resin have increased with the improvement of the performance of the resin. Recently, connection structures using resin as an adhesive have increased not only in conventional die bonding, that is, bonding between the surface opposite to the circuit forming surface of a semiconductor device and a board, but in face-down bonding, that is, bonding in which the circuit forming surface of a semiconductor device faces the board.
As the resin, thermosetting, thermoplastic or ultraviolet-setting epoxy resin a is generally used. When conductivity is required, the resin is mixed with conductive particles made of metal or carbon or particles made by covering resin balls with metallic films.
When a component is found to be defective, in testing in situ on the board after bonding, it is necessary to remove that component individually, in order to avoid wastage of the whole board and other components attached to it.
When the component device is bonded by solder, it can be easily removed by melting the solder. Moreover, it is comparatively easy to return the solder state on the board almost to the original state before bonding by sucking residual solder.
However, resin bonding is not so easy to disconnect and remove as solder bonding. Especially, it is difficult to remove residual resin from the surface of a board. As a means for avoiding this, a solution is proposed in JP-A-63-157429 (1988) in which a die bonding area is constituted by two layers of resin and solder respectively, to permit bonding with the resin and removal by melting of the solder.
As a method for removing semiconductor devices with a bonding structure of only resin, JP-A-63-201627 (1988) and JP-A-2-25042 (1990) disclose techniques using the property that even thermosetting resin is softened at a high temperature. These publications describe the removal of a semiconductor device by heating and softening the resin. However, the removal of residual resin from the board, which is the biggest problem arising in component removal with bonding structures using resin, is not discussed in the prior art.
Solvent is generally used to remove residual resin. Organic acid is used as the solvent to swell the residual resin. Then the resin is wiped away by means of a cotton cleaner. However, solvent cannot be used to remove residual resin on a wiring board which is to receive another component at the same location. It takes much time to swell resin. Moreover, unless the solvent is completely removed from the board after removing the resin, corrosive matter is left in bonding areas. Thus, a problem arises that the reliability of the subsequent bonding is impaired.
There is also known a method for removing residual resin by oxidizing and decomposing the resin by heating or the like in an oxygen atmosphere. Because resin is a macromolecular compound, it easily causes oxygen deficiency and thus carbonization is difficult to avoid. As a result, not only can the resin not be removed, but also a problem occurs that the residual resin impairs the electrical insulation.
In the light of the present invention as described below, it is mentioned for completeness that ablation of resin, i.e. its removal with leaving residual products, is known in a process of etching polyimide films, e.g. in the manufacture of semiconductor devices, using UV radiation (see U.S. Pat. No. 4,508,709). Furthermore, an article in the Japanese Journal "Plasticity & Processing" Vol. 27, No. 307, page 935 is discussed below. It describes generally decomposition of thermoplastic or thermosetting resins, but not specific problems of removal.